Multielectrode Unipolar Voltage Mapping and Electrogram Morphology to Identify Post-Infarct Scar Geometry: Validation by Histology.

OBJECTIVES: This study sought to evaluate the ability of uni- and bipolar electrograms collected with a multielectrode catheter with smaller electrodes to: 1) delineate scar; and 2) determine local scar complexity. BACKGROUND: Early reperfusion results in variable endocardial scar, often overlaid with surviving viable myocardium. Although bipolar voltage (BV) mapping is considered the pillar of substrate-based ablation, the role of unipolar voltage (UV) mapping has not been sufficiently explored. It has been suggested that bipolar electrograms collected with small electrode catheters can better identify complex scar geometries. METHODS: Twelve swine with early reperfusion infarctions were mapped with the 48-electrode OctaRay catheter and a conventional catheter during sinus rhythm. BV electrograms with double components were identified. Transmural (n = 933) biopsy specimens corresponding to mapping points were obtained, histologically assessed, and classified by scar geometry. RESULTS: OctaRay UV (UVOcta) and BV (BVOcta) amplitude were associated with the amount of viable myocardium at a given location, with a stronger association for UVOcta (R2 = 0.767 vs 0.473). Cutoff values of 3.7 mV and 1.0 mV could delineate scar (area under the curve: 0.803 and 0.728 for UVOcta and BVOcta, respectively). The morphology of bipolar electrograms collected with the OctaRay catheter more frequently identified areas with 2 layers of surviving myocardium than electrograms collected with the conventional catheter (84% vs 71%). CONCLUSIONS: UV mapping can generate a map to delineate the area of interest when using a multielectrode catheter. Within this area of interest, the morphology of bipolar electrograms can identify areas in which a surviving epicardial layer may overlay a poorly coupled, potentially arrhythmogenic, endocardium.

Coronary atherosclerotic plaque burden and composition by CT angiography in Caucasian and South Asian patients with stable chest pain.

AIMS: South Asian (SA) patients are known to have an increased incidence of acute cardiovascular events compared with Caucasians. The aim of this observational study was to compare the prevalence of coronary stenoses, the amount and composition of coronary atherosclerosis in a cohort of Caucasian and SA patients with stable chest pain, in non-acute settings. METHODS AND RESULTS: The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki. In 963 consecutive Caucasian and SA patients undergoing coronary computed tomography angiography, atherosclerotic plaques were quantified using a semi-automated algorithm. The vessel per cent diameter and area stenosis were measured. Plaque composition was examined from the measurement of calcified, non-calcified, and total plaque burden. There were 420 Caucasian (238 males) and 543 SA (297 males) patients. Caucasian patients were older than SA patients (54.39 ± 11.65 vs. 49.83 ± 11.03 years) and had lower prevalence of diabetes (13.13 vs. 32.41%) and hyperlipidaemia (56.90 vs. 68.51%) (all P-values <0.001). After adjusting for differences in cardiovascular risk factors, there were no differences in per cent diameter and area stenosis, and no difference in the proportions of patients with one-, two-, or three-vessel disease. There was no difference in total plaque burden; however, the per cent non-calcified plaque composition was lower in Caucasians compared with SA (80.95 vs. 90.42%; P-value <0.001). CONCLUSION: This study conducted in non-acute settings showed an ethnic difference in composition of coronary atherosclerotic plaque with lower non-calcified composition in Caucasian patients compared with SA patients, which was independent of age, diabetes, hyperlipidaemia, and the other available cardiovascular risk factors.